What Makes a Great Tumblr a Great Book?

When Yahoo bought Tumblr this summer, it further signaled a move into digital content. But it may want to consider print as well: At least 70 books have been spun off of Tumblrs, according to founder David Karp, and more surely will follow. Four Tumblr turned book insiders explain what makes a winner:

"There are a lot of awesome Tumblrs, but they post 50 jokes and that's the life of it. You have to maintain that audience online so that in a year or two, when the book is published, they're still there watching." —Kate McKean, Morhaim Literary Agency, Agent for Sh*t Rough Drafts (Spring, 2014)

"I still go for the same thing I go for anywhere, which is voice and not just a collection of things that happen to be shareable. If you look at which deals did best, I imagine that voice would be the denominator." —Jason Ashlock,Movable type, agent for Stuff Hipsters Hate (Fall, 2010)

"The Tumblr itself doesn't have a huge following, but it's best when the author does. When the time comes to get a publicity hit, reaching an audience of 748,000 people in one second makes a huge difference." —Samantha Weiner, Abrams Books, editor of Bun B's Rap Coloring and Activity Book (Fall, 2013)

[Illustration by Marek Haiduk]

A version of this article appeared in the September 2013 issue of Fast Company magazine.